Spinal Cord I

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laminae of Rexed and related nuclear groups of grey matter

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Spinal Cord:

Spinal Cord Dr Pankaj Maheria

Spinal Cord:

Spinal Cord Runs through the vertebral canal Extends upper border of the atlas to the junction between the first and second lumbar vertebrae. Regions Cervical Thoracic Lumbar Sacral Coccygeal

Spinal Cord:

Spinal Cord Gives rise to 31 pairs of spinal nerves All are mixed nerves Not uniform in diameter Cervical enlargement: supplies upper limbs Lumbar enlargement: supplies lower limbs

Spinal Cord:

Spinal Cord Conus medullaris - tapered inferior end Ends between L1 and L2 Cauda equina - origin of spinal nerves extending inferiorly from conus medullaris .

Spinal Meninges:

Spinal Meninges Pia mater Arachnoid Dura mater Three membranes surround all of CNS Dura mater - "tough mother", strong Arachnoid meninx - spidery looking, carries blood vessels, etc . Subarachnoid space Pia mater - "delicate mother", adheres tightly to surface of spinal cord

Meninges:

Meninges Spaces Epidural : external to the dura Anesthestics injected here Fat-fill Subdural space : serous fluid Subarachnoid : between pia and arachnoid Filled with CSF

Cross Section of Spinal Cord:

Cross Section of Spinal Cord Anterior median fissure and posterior median sulcus deep clefts partially separating left and right halves

Cross Section of Spinal Cord: Grey matter: :

Cross Section of Spinal Cord: Grey matter: Nerve cells, Neuroglia and blood vessels. H shaped columns Divided into horns Anterior (ventral) horn Posterior (dorsal) horn Lateral horn

Grey matter : Anterior grey column :

Grey matter : Anterior grey column Broad and short Project ventro -laterally Parts : Head Base More broad in cervical and lumbo-scral region

Grey matter : Posterior grey column :

Grey matter : Posterior grey column Extends dorso -laterally close to postero -lateral sulcus of the Spinal cord Dorso -lateral fasciculus of Lissauer Longer & narrower Parts Base Neck Head Apex

Grey matter : Intermediate region :

Grey matter : Intermediate region B/w anterior and posterior grey columns Lateral horn

Grey matter : Central canal:

Grey matter : Central canal Ependyma Contains CSF Coninuous above with cavity of 4 th ventricle throught central canal of medulla oblongata Terminal ventricle Position Ventral - cervical & thoracic Central – lumbar Dorsal – caudal segments Substanti gelatinosa centralis

Cross Section of Spinal Cord:

Cross Section of Spinal Cord White matter Myelinated axons Divided into three columns ( funiculi ) Ventral Dorsal Lateral Each of these divided into sensory or motor tracts

PowerPoint Presentation:

Characteristic features of spinal segments as seen In transverse sections at various eve sot e spinal cord Features Levels Cervical Thoracic Lumbar Sacral Outline of section Oval Oval to circular Nearly circular Circular to quadrilateral Reticular formation Well develop Poor develop Absent Absent Amount of white matter Massive ++++ Large +++ Less ++ + Posterointermediate sulcus Present Present in upper seven Absent Absent

PowerPoint Presentation:

Characteristic features of spinal segments as seen In transverse sections at various eve sot e spinal cord Features Levels Cervical Thoracic Lumbar Sacral Grey matter Large Small large Relatively large Posterior horn Slender and extends far posteriorly Slender Bulbous Massive Anterior horn Massive Slender Bulbous Massive lateral horn Absent Present Present in L1 & 2 Present in S 2 3 & 4

Cross section of Spinal Cord:

Cross section of Spinal Cord Commissures : connections between left and right halves Gray with central canal in the center White

Cross section of Spinal Cord:

Cross section of Spinal Cord Roots Spinal nerves arise as rootlets then combine to form dorsal and ventral roots. Dorsal and ventral roots merge laterally and form the spinal nerve.

Columnar arrangement of neurons in Anterior grey columns:

Columnar arrangement of neurons in Anterior grey columns Three groups Medial group Lateral group Central group

Lateral group:

Lateral group Cervical and lumbo -sacral enlargements Supplies the limb muscles Division : Ventro –lateral Dorso-Iateral Retro- dorsolateral parts.

Medial group:

Medial group Extends along most of the length of the cord Ventro -medial and Dorso -medial

Posterior Grey Columns:

Posterior Grey Columns Two types of nerve cells- Interneurons Tract cells

Columnar arrangement of neurons in Posterior grey columns:

Columnar arrangement of neurons in Posterior grey columns Four sets Substantia gelatinosa Nucleus propriu Nucleus dorsalis (Clarke's column ) Visceral afferent nucleus

Substantia gelatinosa:

Substantia gelatinosa Composed of numerous small and medium sized interneurons . Caps the apex of the grey column Extends along the entire length of the spinal cord. Nucleus of spinal tract of the trigeminal nerve

Nucleus proprius:

Nucleus proprius Deep to the substantia gelatinosa Occupies the head and neck of posterior grey column Extends along the entire length of the spinal cord. composed of interneurons and tract cells Fibres enter the nucleus proprius from both lateral and medial divisions of the dorsal nerve roots.

Nucleus dorsalis (Clarke's column ):

Nucleus dorsalis (Clarke's column ) Occupies: Medial part of the base of the posterior grey column Projects somewhat in the posterior funiculus Extends: C5 to L2 to L3 segments of the cord Consists: Interneurons and tract cells.

Visceral afferent nucleus:

Visceral afferent nucleus Ill defined elongated nucleus at the base of the posterior grey column. Extends: T1 to L2 segments and from S2 to S4 segments of the spinal cord

Intermediate region of Spinal grey matter:

Intermediate region of Spinal grey matter

Arrangements of neurons with functional status:

Arrangements of neurons with functional status Lateral horn of the intermediate region Extends From T I to L2 segments of the cord, Composed: Intermedio - lateral Intermedio - medial columns of cells Which act as preganglionic neurons of sympathetic system ( thoraco-Iumbar outflow).

PowerPoint Presentation:

Summary of the various cell columns/nuclei in different horns (grey columns) of the spinal cord. Cell Columns/Nuclei Extend In The Cord Functions Posterior Horn Substantia Gelatinosa E n tire cor d Rel ay n ucl e u s for pain and t e mperature , modification of tr a n s mi ss ion of se n so ry input Nucleus Dorsalis (Clarke's Column) (8 T o L2 Or Ll G i ves o rigin to axon s w hi c h form Poster ior S pino ce r e b e ll a r Tract Nucleus Proprius Entire co rd Contains i nt e rnunci a l neuron s f or sp in a l refl exes a n d secon d order sensory n e u rons o f th e Vent r a l S pinothalamic Tract Visceral Afferent Nucleus T1 To L 2 Or Ll A nd 52 To 54 Rel ay nu cleus f o r v i sce ral a ff e rent i mpu l ses Anterior Horn Medial Motor Cell Column En ti re cord Supplies muscl es o f the n eck a nd trunk Lateral Motor Cell Column C4 To T1 And L2 To 53 Supp li es muscles of th e ex tr emities Phrenic Nucleus C3 To C 5 M otor inn ervat io ns of th e diaphragm Spinal Accessory Nucleus C 1 To C 5 Origin o f s pina l r oot of accessory n erve Lateral Horn Intermediolateral Cell Column T1 To L 2 Or L3 Sourc e of preganglionic sympathe tic fibre s Sacral Parasympathetic Nucleus S2 T o S4 Sou r ce of preganglionic parasympathetic fibres

PowerPoint Presentation:

Sub

Lamina of Rexed:

Lamina of Rexed Lamina I Posteromarginal Nucleus Lamina II Substantia Gelatinosa of Rolando Lamina III Lamina IV, V, VI ----- Nucleus Proprius Lamina VII Intermediate Grey I ntermediolateral cell column (ILM) Clarke’s column (Nucleus dorsalis ) I ntermediomedial cell column (IMM) Lamina VIII Lamina IX ---------- Anterior Horn (Motor) Cell Lamina X ----------- Gray Commissure

laminae of Rexed and related nuclear groups.:

laminae of Rexed and related nuclear groups.

Lamina I:

Lamina I AKA: lamina marginalis or the layer of Waldeyer Receives incoming dorsal root fibers and collateral branches as well Larger neurons contribute axons to Contralateral Spinothalamic Tract

Lamina II:

Lamina II AKA: Substantia Gelatinosa Involved in Pain interpretation Receives incoming input from dorsal root axons & descending input from reticular formation of the medulla Efferent axons travel up & down several segments to make contactwith other areas of the dorsal horn

Lamina III:

Lamina III Contains larger, less densely packed cells than lamina II Receives primary afferents from dorsal root fibers Neurons considered as a part of nucleus proprius

Lamina IV:

Lamina IV Contains a variety of cell types that have more myelin than any other lamina Some tract cells originate here, axons cross the midline and enter the contralateral Spinothalamic Tract , also sends contacts to layers II and III Receives afferents from dorsal roots via the dorsal funiculus At rostral end of spinal cord, laminas I-IV become continuous with the spinal trigeminal nucleus

Lamina V - VI:

Lamina V - VI Origination of tract cells, similar to lamina IV, these tracts cells are also known as the Nucleus Proprius (e.g. spinal thalamic tract or anterolateral system; pain and temperature, some tactile) Receives afferent input from dorsal roots and descending fibers, most importantly Corticospinal

Lamina V - VI:

Lamina V - VI Laterally, gray matter at base of dorsal horn mixes with white matter from lateral funiculus , this region is called reticular formation. It is noticeable in the cervical region reticular formation

Lamina VII:

Lamina VII The largest region, occupies most of ventral horn &intermediate zone Projects long axons that connect to other grey matter segments of the cord Some columns do not fit into the lamina scheme, and have individual designations: Nucleus dorsalis ( Clarke ) Intermediolateral cell column Intermediomedial cell column Sacral autonomic nucleus

Lamina VII:

Lamina VII Nucleus dorsalis of Clark AKA nucleus thoracicus is located medial & ventral to the dorsal horn in T1-L3 Composed of large neurons & axons that form the dorsal spinocerebellar tract on the ipsilateral side

Lamina VII:

Lamina VII Intermediolateral cell column is located at the lateral portion of the intermediate zone. Responsible for the formation of the lateral horn in T1 – L2 Consists of cell bodies of sympathetic preganglionic neurons

Lamina VII:

Lamina VII Intermediomedial cell column is located lateral to lamina X. Not seen in all cord sections. Receives primary afferent fibers from dorsal root and has been implicated in visceral reflexes

Lamina VII:

Lamina VII Sacral autonomic nucleus is located in the lateral part of lamina VII in S2-S4 segments Consists of preganglionic para - sympathetic neurons

Lamina VIII:

Lamina VIII Located on the medial aspect of the ventral horn Efferent projections both ipsilaterally and contralaterally to the same and nearby segmental levels to lamina VII & IX Site of termination for descending fibers, including the vestibulospinal and reticulospinal tracts

Lamina IX:

Lamina IX Consists of columns of neurons embedded in either lamina VII or VIII Cells include alpha and gamma motor neurons, which axons exit via the ventral roots and innervate striated muscle. Smaller neurons contribute axons to the ventral fasciculus proprius Four columns of motor neurons can be identified within this lamina; Ventromedial Ventrolateral Dorsolateral Central Each has characteristic dendritic features

Lamina IX:

Lamina IX Ventral gray columns in lamina IX have somatotopic arrangement: Medial areas innervate the axial musculature Lateral areas innervate the limbs muscles

PHRENIC NUCLEUS:

PHRENIC NUCLEUS The phrenic nucleus is located in the ventromedial area of the ventral horn in C2-C5 segments. It receives bilateral innervation from the solitary nucleus of the medullary region, via solitary tract. This nucleus is responsible for the innervation of the diaphragm

SPINAL ACCESSORY NUCLEUS :

SPINAL ACCESSORY NUCLEUS The spinal accessory nucleus (cranial nerve XI) is located in the lateral area of vental horn in C1-C5 segments. Corticospinal tract innervates this nucleus bilaterally. This nucleus is also responsible for the innervation of the trapezius & sternocleidomastoid muscles ( ipsilaterally )

Lamina IX:

Lamina IX Nucleus of Onuf Located ventrolaterally in S1-S2 spinal segments Supplies muscles of the pelvic floor, including striated muscle sphincters for urinary and fecal continence

Lamina X:

Lamina X Surrounds the central canal, and includes the ventral gray commissure Contains relatively small neurons, radial neuroglia cells & decussating axons Some dorsal root afferents terminate here

PowerPoint Presentation:

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